// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "cc/trees/occlusion.h"

#include "cc/base/math_util.h"
#include "ui/gfx/geometry/rect.h"

namespace cc {

Occlusion::Occlusion()
{
}

Occlusion::Occlusion(const gfx::Transform& draw_transform,
    const SimpleEnclosedRegion& occlusion_from_outside_target,
    const SimpleEnclosedRegion& occlusion_from_inside_target)
    : draw_transform_(draw_transform)
    , occlusion_from_outside_target_(occlusion_from_outside_target)
    , occlusion_from_inside_target_(occlusion_from_inside_target)
{
}

Occlusion Occlusion::GetOcclusionWithGivenDrawTransform(
    const gfx::Transform& transform) const
{
    return Occlusion(
        transform, occlusion_from_outside_target_, occlusion_from_inside_target_);
}

bool Occlusion::HasOcclusion() const
{
    return !occlusion_from_inside_target_.IsEmpty() || !occlusion_from_outside_target_.IsEmpty();
}

bool Occlusion::IsOccluded(const gfx::Rect& content_rect) const
{
    if (content_rect.IsEmpty())
        return true;

    if (!HasOcclusion())
        return false;

    gfx::Rect unoccluded_rect_in_target_surface = GetUnoccludedRectInTargetSurface(content_rect);
    return unoccluded_rect_in_target_surface.IsEmpty();
}

gfx::Rect Occlusion::GetUnoccludedContentRect(
    const gfx::Rect& content_rect) const
{
    if (content_rect.IsEmpty())
        return content_rect;

    if (!HasOcclusion())
        return content_rect;

    gfx::Rect unoccluded_rect_in_target_surface = GetUnoccludedRectInTargetSurface(content_rect);
    if (unoccluded_rect_in_target_surface.IsEmpty())
        return gfx::Rect();

    gfx::Transform inverse_draw_transform(gfx::Transform::kSkipInitialization);
    bool ok = draw_transform_.GetInverse(&inverse_draw_transform);
    // TODO(ajuma): Skip drawing layers with uninvertible draw transforms, and
    // change this to a DCHECK. crbug.com/517170
    if (!ok)
        return content_rect;

    gfx::Rect unoccluded_rect = MathUtil::ProjectEnclosingClippedRect(
        inverse_draw_transform, unoccluded_rect_in_target_surface);
    unoccluded_rect.Intersect(content_rect);

    return unoccluded_rect;
}

gfx::Rect Occlusion::GetUnoccludedRectInTargetSurface(
    const gfx::Rect& content_rect) const
{
    // Take the ToEnclosingRect at each step, as we want to contain any unoccluded
    // partial pixels in the resulting Rect.
    gfx::Rect unoccluded_rect_in_target_surface = MathUtil::MapEnclosingClippedRect(draw_transform_, content_rect);
    DCHECK_LE(occlusion_from_inside_target_.GetRegionComplexity(), 1u);
    DCHECK_LE(occlusion_from_outside_target_.GetRegionComplexity(), 1u);
    // These subtract operations are more lossy than if we did both operations at
    // once.
    unoccluded_rect_in_target_surface.Subtract(
        occlusion_from_inside_target_.bounds());
    unoccluded_rect_in_target_surface.Subtract(
        occlusion_from_outside_target_.bounds());

    return unoccluded_rect_in_target_surface;
}

bool Occlusion::IsEqual(const Occlusion& other) const
{
    return draw_transform_ == other.draw_transform_ && occlusion_from_inside_target_ == other.occlusion_from_inside_target_ && occlusion_from_outside_target_ == other.occlusion_from_outside_target_;
}

std::string Occlusion::ToString() const
{
    return draw_transform_.ToString() + "outside(" + occlusion_from_outside_target_.ToString() + ") inside(" + occlusion_from_inside_target_.ToString() + ")";
}

} // namespace cc
